1. Field of the Invention
The present invention is related to an all-optical OR gate embodied by using the gain saturation and wavelength conversion characteristics of semiconductor optical amplifier (SOA). More particularly, the present invention is related to a technique to embody an all-optical OR gate that performs all-optical logic operation by utilizing optical signals transmitted from arbitrary points of optical circuits such as optical computing circuits as a pump signal and a probe signal.
2. Description of the Related Art
In recent years, needs for high speed and large capacity of optical systems have been increased dramatically. Since the future information networks have to be prepared for multimedia services like voice signals, stationary images, and animated images, the information processing capacity of backbone networks is expected to increase from several hundred Gbit/s to several Tbit/s. Therefore, in order to transmit, process, and communicate large capacity of data, all-optical signal processing techniques have emerged as the core technology.
Particularly, since all-optical logic operations can avoid the cumbersome electro-optic conversion, it is considered as the core technology for all-optic signal processing systems. Therefore, technologies of all-optical logic gates are being developed actively in the fields of optical computing and all-optical signal processing.
Up to now, all-optical logic gate s for ultra-high speed optical information processing have been utilizing mainly the non-linear characteristics of semiconductor optical amplifiers (SOAs). For examples, all-optical logic gates are relying on mechanisms such as four-wave mixing (FWM), cross gain modulation (XGM), cross phase modulation (XPM) cross-absorption modulation (XAM), or combinations of these.
Therefore, all-optical OR gates in the prior art were realized by methods using ultra fast nonlinear interferometer (UNI) utilizing the nonlinear gain and refractive index change of semiconductor optical amplifier (SOA) [Refer to N. S. Patel, K. L. Hall, and K. A. Rauschenbach, Opt. Lett. Vol. 21, 1466 (1996)] and integrated SOA-based Michelson interferometer [Refer to T. Fjelde, D. Wolfson, A. Kloch, C. Janz, A. Coquelin, I. Guillemot, F. Gaborit, F. Poingt, B. Dagens, and M. Renaud, Elecronic Letters, Vol. 36, 813 (2000)].
However, in order for a plurality of all-optical logic gates such as AND, NAND, OR, NOR, and XOR to be used in complicated optical circuits of optical computing or all-optical signal processing systems, each of all-optical logic gates is desired to embody on the same operational principle for a favorable system constitution. By utilizing the gain saturation and the wavelength conversion characteristics of SOA, all-optical NOR, XOR, and NAND as well as all-optical OR gate in accordance with the present invention could be embodied. [For all-optical NOR, refers to Y. T. Byun, S. H. Kim, D. H. Woo, D. H. Kim, and S. H. Kim, New Physics, Vol. 40, 560 (2000).]
The present invention is to solve the above mentioned problems in the prior art. It is an object of the present invention to provide a device embodied for all-optical OR gates by using the characteristics of gain saturation and wavelength conversion of semiconductor optical amplifiers(SOAs).
To achieve the aforementioned object, the present invention provides with all-optical OR logic device in which 2.5 Gbit/s input signal generates four logic signals by way of mode-locked fiber laser and multiplexing techniques and then these logic signals and the probe signal are under the effect of the gain saturation and the wavelength conversion characteristics while transmitting through the semiconductor optical amplifier (SOA).